1. Field of the Invention
The present invention relates to a liquid crystal display device having a plurality of display areas, and also to a method of driving the liquid crystal display device.
2. Description of the Related Art
A display device for use in an electric apparatus such as a pager or a calculator has a row of picture sections for displaying a row of characters forming an information item such as a telephone number. FIG. 9 shows one example of display devices of this type. As shown in FIG. 9, this display device comprises a first display area 1, a second display area 2, a driving circuit 3, a circuit board 4, a first flexible substrate 5, a second flexible substrate 6, first row lines 7, a third flexible substrate 8, second row lines 9, and a fourth flexible substrate 10.
Also, the display device comprises a pair of glass substrates and a liquid crystal. The glass substrates are spaced apart from each other, defining a space between them. The liquid crystal is sealed in the space between the glass substrates. The first display area 1 has eight picture sections 1a to 1h which are arranged in a row, spaced at regular intervals. Similarly, the second display area 2 has eight picture sections 2a to 2h which are arranged in a row, spaced at regular intervals. The row constituted by the picture sections 1a to 1h and the row constituted by the picture sections 2a to 2h are arranged, end to end, along a straight line.
Each of the picture sections 1a to 1h and 2a to 2h has eight scan electrodes and five signal electrodes. The scan electrodes are arranged on the first glass substrate, extending parallel to one another at right angles to the row of the picture sections 1a to 1h and 2a to 2h. The direction in which the scan electrodes extend will be referred to as "row direction" hereinafter. On the other hand, the signal electrodes are arranged on the second glass substrate, extending parallel to one another and parallel to the row of the picture sections 1a to 1h and 2a to 2h. The direction in which the signal electrodes extend will be referred to as "column direction" hereinafter. Thus, the eight scan lines intersect at right angles, forming 40 intersections, and the liquid crystal has 40 portions which are sandwiched between the intersecting parts of the signal and scan electrodes which function as pixels.
The driving circuit 3 is a rectangular semiconductor chip which is designed to drive the first display area 1 and the second display area 2. The circuit board 4 is provided near the lower sides of the display areas 1 and 2. The driving circuit 3 is mounted on the circuit board 4.
The driving circuit 3 has signal terminals DS1 to DS40 and scan terminals DC1 to DC16. The signal terminals DS1 to DS40 are provided at the front side of the driving circuit 3, the scan terminals DC1 to DC8 at the left side of the circuit 3, and the scan terminals DC9 to DC16 at the right side of the circuit 3. The signal terminals DS1 to DS40 are connected to the signal terminals PS1 to PS40 of the first display area 1 by the first flexible substrate 5, and also connected to the signal terminals PS41 to PS80 of the second display area 2 by the second flexible substrate 6. The second flexible substrate 6 partly overlaps the first flexible substrate 5 at a region close to the signal terminals DS1 to DS40 of the driving circuit 3. The overlapping part of the second flexible substrate 6 is electrically insulated by an insulating member (not shown) mounted on the first flexible substrate 5.
The first row lines 7 are electrically connected at one end to the scan terminals DC1 to DCS, and at the other end to one end to the third flexible substrate 8. The other end of flexible substrate 8 is connected to the scan terminals PC1 to PC8 of the picture sections 1a to 1h. Similarly, the second row lines 9 are electrically connected at one end to the scan terminals DC9 to DC16, and at the other end to the further flexible substrate 10. The other end of the fourth flexible substrate 10 is connected to the scan terminals PC9 to PC16 of the picture sections 2a to 2h.
In operation, scan signals output from the scan terminals DC1 to DC8 are sequentially supplied to the scan terminals PC1 to PC8 of the picture sections 1a to 1h. At the same time, segment signals are sequentially output from the signal terminals DS1 to DS40 of the driving circuit 3 and supplied to the signal terminals PS1 to PS40 of the picture sections 1a to 1h. The picture sections 1a to 1h of the first display area 1 display characters. Next, scan signals are output from the scan terminals DC9 to DC16 of the display circuit 3 to the scan terminals PC9 to PC16 of the picture sections 2a to 2h. Simultaneously, segment signals are sequentially output from the signal terminals DS1 to DS40 of the driving circuit 3 and supplied to the signal terminals PS41 to PS80 of the picture sections 2a to 2h. The picture sections 2a to 2h of the second display area 2 display characters.
The display circuit 3 needs to have only half the number of signal terminals which are required to make the picture sections 1a to 1h and 2a to 2h display characters. Namely, a single driving circuit suffices to drive two display areas 1 and 2.
In the conventional display device shown in FIG. 9, the signal terminals DS1 to DS40 of the driving circuit 3 are connected to the signal terminals PS1 to PS40 of the first display area 1 by the first flexible substrate 5, and also to the signal terminals PS41 to PS80 of the second display area 2 by the second flexible substrate 6. Inevitably, the lines of the first flexible substrate 5 and those of the second flexible substrate 6 overlap in the vicinity of the signal terminals DS1 to DS40 of the driving circuit 3 to each other. An insulating member must therefore be interposed between the first flexible substrate 5 and the second flexible substrate 6. To connect the signal terminals DS1 to DS40 to the display areas 1 and 2, there are required three components--that is, two flexible substrates 5 and 6 and one insulating member (not shown). Furthermore, it is cumbersome to connect the terminals DS1 to DS40 to the display areas 1 and 2, unavoidably reducing the productivity of the conventional device.
Since the lines of the first flexible substrate 5 intersect with those of the second flexible substrate 6 near the signal terminals DS1 to DS40 of the driving circuit 3, the driving circuit 3 and the display areas 1 and 2 cannot be mounted on the same board. The driving circuit 3 must be mounted on the circuit board 4, while both display areas 1 and 2 must be mounted on another board. Therefore, not only two flexible substrates 5 and 6 are required to connect the signal terminals DS1 to DS40 to the signal terminals PS1 to PS80, but also two other flexible substrates 8 and 10 need to be used to connect the scan terminals DC1 to DC16 of the display circuit 3 to the scan terminals PC1 to PC16 provided in the display areas 1 and 2.
Hence, the conventional display device needs to have comparatively many connecting components and, therefore, be manufactured in many steps. As a consequence, the productivity of the display device is more reduced still.